While efforts have been undertaken to increase the ease with which analytes from body fluids, such as glucose, can be periodically monitored. No proposed solution has proved entirely satisfactory. The present invention provides a new monitoring device which allows convenient such monitoring with reduced pain.
Diabetes mellitus, a disease in which the pancreas fails to produce insulin or cells fail to respond to insulin for cellular metabolism of glucose, is a world-wide public health problem in terms of loss of quality of life and corresponding cost of care.
The World Health Organization estimates, as of 1994, there are 110 million diabetics worldwide with 14-16 million in the USA. This number is increasing and expected to double by 2030. Approximately 12-14 million diabetics are classified as noninsulin dependent, or Type II, diabetics who can control their glucose levels by changes in life style, by the use of medication or by the infrequent use of insulin. For approximately 1-2 million diabetics, classified as Type I diabetics, injections of insulin are needed to maintain glucose levels. Data from the Diabetes Control and Complications Trial (DCCT), reported in 1993, show that the quality of life may significantly be improved for people with diabetes if good control of blood sugar (glucose) levels is maintained. Thus, there is a need for frequent and accurate self-testing of glucose.
To meet this need, the most widely used, reliable and accurate method is a direct assay for glucose in a small amount of, typically, venous blood. Hand-held instruments, which measure the amount of glucose based on the interaction of glucose with reagents predeposited on test strips, are now widely available. Typically these instruments detect the amount of glucose in blood to plus or minus 4%, based on specific enzymatic reactions using microliter samples of blood.
While the chemistry for these test are reliable, and the manufacturers of the test strips have demonstrated good quality control, current self-testing remains a conscious process in which the diabetic must elect to take a blood sample and do the assay protocol for the hand-held instrument of choice. The primary failure for diabetics to do frequent self-testing for blood glucose levels, as recommend by the conclusions of the DCCT, is the pain associated with obtaining blood samples on a frequent schedule as well as the inconvenience of this, particularly in public places.
To reduce pain and inconvenience, blood glucose assays based on interstitial fluid, on transport through the skin (iontophoresis) and by implanted glucose sensors are technologies currently proposed, in development, or FDA approved. Cygnus, Inc. (Redwood, Calif.) has received FDA approval for the xe2x80x9cGlucoWatchxe2x80x9d a noninvasive glucose testing device that is based on electrode-driven iontophoresis. MiniMed Inc. (Sylmar, Calif.) has developed and received FDA approval of an invasive glucose sensor which may be used to monitor glucose continuously for up to three days.
Provided here is a reliable and reduced pain or essentially pain-free approach to frequent glucose monitoring, or for monitoring of any blood metabolite. The use of very small samples, microliter or less, combined with a sensitive and reliable chemical test for the metabolite in an automated device allows for metabolite monitoring with convenience, comfort and reduced pain. The automation of the glucose testing offers an inherent psychological advantage in that the occurrence of the testing is essentially unknown to the user. Automation offers a further advantage in that a specific program can be applied for frequent testing based on the user""s life style. With the present invention, a large number, for example 120, of blood tests can be provided per unit, thus allowing frequent testing for up to a month period. Furthermore, miniaturization allows for the design of a small device that can be in the shape of, e.g., a xe2x80x9cwatchxe2x80x9d, allowing for portability and unusual convenience.
The invention provides an analyte monitoring device having a housing, the device comprising: a plurality of needles, each having a tip, a retracted position, a position wherein the tip is extended from the housing a distance adapted to pierce skin; an electrically or spring powered needle pushing apparatus movable to separately engage each of the needles to move each from the retracted position to the extended position; an energy source located within the housing; a plurality of analysis sites comprising an analysis preparation, each adapted to receive liquid from the needles to wet the analysis preparation; one or more light sources adapted to direct light at the analysis sites; one or more light detectors adapted to receive light from the analysis sites; and a processor.
The invention further provides an analyte monitoring device having a housing, the device comprising: (a) a plurality of needles, each having a tip, a retracted position, a position wherein the tip is extended from the housing a distance adapted to pierce skin; (b) an electrically or spring powered needle pushing apparatus movable to separately engage each of the needles to move each from the retracted position to the extended position; (c) an energy source located within the housing; (d) a plurality of evacuated sites, each adapted to engage an associated needle during or following needle movement to apply the vacuum to the needle while it is in an extended position; and (e) a processor.
An analyte monitoring device having a housing, the device comprising: one or more needles, each having a tip, a retracted position, a position wherein the tip is extended from the housing a distance adapted to pierce skin; and a light source fixed to the housing aligned to heat a tissue aligned to intercept the extended positions of the needles.